<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <script>
    let sumBer = ['12', '42', '564', '56', '45', '56', '12', '86', '35', '56',
      '35', '98', '78', '78', '12', '75', '12', '78',
      '78', '56', '45', '6', '12', '63',]
    let result = []
    for (var i = 0; i < sumBer.length; i += 4) {
      result.push(sumBer.slice(i, i + 4))
    }
    console.log(result[1])
  </script>
</body>

</html>